The southbound toll at the Dartford Crossing between Kent and Essex could be scrapped to help cut congestion.
Transport Minister Sadiq Khan said one-way charging was one of two options being considered to help traffic flow and improve safety.
In a letter to Hornchurch MP James Brokenshire, Mr Khan said the other scenario would see the toll layout changed and new technology introduced. He said each option had the potential to cut traffic.
He received the letter from Mr Sadiq after he wrote to the government asking them to examine the impact a recent power cut, which led to motorists not being charged, had on traffic levels.
Mr Brokenshire said: “The information clearly points to the fact that the tolls themselves are adding to congestion on this piece on the M25.
“It’s one of the worst congested roads as anybody who’s been driving around in this area for some time will tell you.”
He added: “Maybe it’s just that the information is now there that has convinced them that they do need to take action to listen to the motorists who have complained about the problems and delays.”
In August the AA said there were noticeably more delays on the M25 since November 2008 when the crossing charge was raised from £1 to £1.50 for cars.
There is no charge to use the Dartford Tunnel and QEII bridge between 2200 and 0600.
A spokesman for the Department for Transport confirmed it was looking in more detail at the potential options for tackling congestion and improving capacity across the River Thames, which included one-way tolling.